Search

Progress over the last few years designing new materials for organic bulk heterojunction (BHJ) solar cells has been enormous with efficiencies reaching more than 13%1 . However, a multitude of combinations exist on how to blend donors and acceptors, with a wide variety of processing options, rendering materials selection and testing an intricate task. Indeed, detailed fundamental understanding between phase behaviour and BHJ properties is still lacking, drastically limiting, among many things, device reproducibility and general progress in the field2 . Despite the apparently chaotic scenario, a simple pathway is here presented to predict BHJs microstructure and phase morphology in OPV using PCE11 (i.e. PffBT4T-2O) and poly(2,5-bis(3-tetradecyllth-iophen-2-yl) thieno[3,2,-b]thiophene) (i.e. pBTTT) :fullerene blends as model systems. We confirm that differential scanning calorimetry assist in establishing temperature/composition diagrams. These can be read as solidification road-maps to predict BHJ morphologies, by far analogy with metallurgy3,4. Coexistence of relatively phase-pure fullerene4 domains together with a finely intermixed phase has already been proved via several visualisation techniques and it is regarded as a requirement for high performances5,6 . Exploring a range polymer-to-fullerene combinations, different morphology scenarios have been targeted: complete phase separation, co-crystal and fullerene intercalation, disordered intermix. Thereby the investigative focus is on the role played by the intermixed phases, discerning between ordered and disordered ones. Indeed, considering the results on the prototypical P3HT blends and the presented pBTTT, the proposed approach is extended to the class of high-performance D-A polymers system, such as PCE11: PCBM ([6,6]-Phenyl-C61-butyric acid methyl ester). Undeniably phase diagrams may predict phase separation, though hereby an approach is offered to manipulate the length scale of each component-rich domain and the intermixed matrix surrounding it. In this frame the solidification processes are investigated via in-situ spectroscopy, in order to reveal the -HJ aggregates formation mechanisms. “Rebus sic stantibus”, this work offers a platform to disentangle effects of miscibility, processing and final device performance.

Cardiac hypertrophy leading to heart failure remains a leading cause of morbidity and mortality in the 21st century despite major therapeutic advances. Improved understanding of novel molecular and cellular processes contributing to cardiac hypertrophy therefore continues to be important. Cyclin-dependent Kinase 9 (CDK9), part of a family of proteins controlling cell cycle and growth, has emerged as one such potential candidate over the last 5 years. CDK9 is the catalytic subunit of the CDK9/CyclinT complex and acts by phosphorylating the carboxy-terminal domain of RNA polymerase II. Hypertrophic signals, such as Endothelin-1 (ET-1) and phenylephrine, have been shown to cause CDK9 activation leading to a hypertrophic response in cultured mouse cardiomyocytes associated with reactivation of the foetal gene program. CDK9 also forms a complex with GATA4 to play a role in differentiation of mouse ES cells into cardiomyocytes. These findings suggest a specific role for CDK9 in controlling growth and differentiation of cardiomyocytes and merits further study in models where cardiomyocyte differentiation and proliferation are key contributors. In contrast to mammals, zebrafish retain a high cardiomyocyte proliferative capacity throughout their life span and can readily repair following injury. I have examined the role of CDK9 on global and cardiac development in the zebrafish embryo. I have also assessed the impact of CDK9 manipulation on response to ventricle injury using a laser-induced injury model developed and validated as part of my thesis. My findings confirm that normal growth of the embryonic ventricle is associated with a rapid increase in cardiomyocyte number, that was of 50% in the period 96-120 hpf, accompanied by increasing chamber trabeculation. This is also characterized by an increase in the gene expression of most of cardiac development relevant transcription factors, i.e. GATA4, 5 and 6, and MEF2c. The significant reduced cardiovascular function (14% of Ejection Fraction compared to 20% in controls) at 2 h post laser injury in the zebrafish embryonic heart promptly recovers at 24 hour post-laser, accompanied by acceleration of cardiomyocyte proliferation, that increased of 49% in injured ventricles compared to 20% in controls in the period 2-24 h post-laser. Pharmacological and genetic inhibition of CDK9 activity also significantly reduced cardiac growth, cardiomyocyte number, ventricle function and impairs functional recovery following laser injury. Conversely, genetic inhibition of LARP7, a CDK9 repressor, resulted in increased cardiomyocyte number and was associated with full functional and cellular recovery following laser-injury. In conclusion, I have provided evidence, in the zebrafish embryonic heart, that CDK9 plays an important role in cardiac growth and development and impacts significantly on cardiomyocyte proliferation. I have also shown that CDK9 manipulation significantly affects cellular and functional recovery following laser-induced injury. Further studies are required to further define the role of CDK9 and LARP7 in the heart and develop therapeutic strategies using this pathway that could contribute to cellular repair mechanisms in the adult mammalian heart.

Cancer is one of the leading cause of death in the world. Since tumorigenesis was described as a multistep mechanism in 1958 by Foulds, important progresses are obtained in the research field. Through these years many altered mechanisms were discovered revealing a very intricate picture of this disease. Mutations, epigenetic changes, aneuploidy imply severe modifications in naive cellular pathways involved in every feature of cell life. p38 MAPK is a family of kinases composed by four isoforms: alpha, beta, delta and gamma. These kinases are involved in several important cellular pathways, from the differentiation of muscle cells to inflammation and also in cancer progression. The pharmacologic and genetic inhibition of p38 alpha in colorectal cancer cells induced cell cycle arrest, autophagy and then cell death with autophagic features. My PhD project is focused on the understanding the role of p38 alpha in the autophagic activation in colorectal cancer cell lines, finding that its inhibition induced the decrease of HIF-1 alpha protein levels and its glycolytic transcriptional program. Moreover, p38 alpha inhibition trigger the activation of FoxO3A-dependent transcription, which is related to cell cycle arrest, autopahgy and cell death. We checked for other HIF-1 alpha-dependent tumors which shown also overactivation of p38 alpha, such as ovarian cancer and prostate cancer. In these kind of tumors we obtained the same encouraging results. However, in the DU 145 prostate cancer cell line, the inhibition of p38 alpha failed to activate autophagic pathway due to the lack of LKB1 kinase, which is the upstream activator of AMPK. In this cell line the inhibition of p38 alpha triggered apoptotic pathway. Chemoresistance is one of the main obstacle in the treatment of cancer. A part of my PhD project is based on the study of p38 alpha role in cisplatin chemoresistance in colorectal cancer cells. Surprisingly, we found that its inhibition, together with the administration of cisplatin, induced apoptotic cell death in the resistant HT29 cell line and increased the effect of cell death in the responsive HCT116 cell line, through the activation of FoxO3A. All these evidences indicated that inhibition of p38 alpha could be used as a promising therapeutic approaches for colorectal cancer and other malignancy, through the activation of FoxO3A-dependent transcription program.